Substituted oxazolidines

ABSTRACT

The invention relates to novel substituted oxazolidines of formula (I) wherein R 1  and R 2  are simultaneously hydrogen or both together are the identical lower alkyl radical, and to the salts thereof in racemic and chiral form, to a process for the preparation of said compounds, to pharmaceutical compositions containing them, and to the use thereof as medicaments. The compounds have a stimulating effect on beta-adrenergic receptors and can be used, inter alia, for the treatment of diseases associated with reversible obstruction of the respiratory tract, typically asthma and chronic bronchitis, and also for inflammation of different origin.

This is a 371 of PCT/EP94/03937, filed Nov. 28, 1994.

The present invention relates to novel substituted oxazolidines of formula I ##STR2## wherein R₁ and R₂ are simultaneously hydrogen or both together are the identical alkyl radical of up to seven carbon atoms, and to the salts thereof in racemic and chiral form, to a process for the preparation of said compounds, to pharmaceutical compositions containing them, and to the use thereof as medicaments.

EP-A-0 422 889 and FR-A-2 545 482 describe amino-alcohols with stimulant activity on beta-adrenergic receptors.

U.S. Pat. No. 4,407,819 (American Cyanmide Co.) discloses oxazolidines which differ in the orientation of the substituents at the phenyl ring and in the substituents at the oxygen atom in the oxazolidine ring, and which are used as additives for animal feeds.

Throughout this specification, radicals and compounds qualified by the term "lower" will be understood as meaning those that carry up to 7, preferably up to 4, carbon atoms inclusive.

Lower alkyl is typically C₁ -C₄ alkyl such as methyl, ethyl, propyl or butyl. The novel compounds thus comprise all enantiomers, diastereoisomers and mixtures thereof, including racemates

Compounds of formula I within the scope of the invention are preferably obtained in the form of racemates of stereoisomers (R and S), most preferably in chiral R and S form.

Salts of compounds of formula I are preferably pharmaceutically acceptable salts, typically acid addition salts, which are formed, inter alia, with strong inorganic acids such as mineral acids, e.g. sulfuric acid, a phosphoric acid or a hydrohalic acid, with strong organic carboxylic acids such as lower alkanecarboxylic acids, typically acetic acid, or with dicarboxylic acids or unsaturated dicarboxylic acids such as malonic acid, maleic acid or furmaric acid, or with hydroxycarboxylic acids such as tartaric or citric acid, or with sulfonic acids such as lower alkanesulfonic acids or benzenesulfonic acids or substituted benzenesulfonic acids such as methane or p-toluenesulfonic acid, or salts with bases, typically alkali metal or alkaline earth metal salts, e.g. sodium, potassium or magnesium salts, pharmaceutically acceptable transition metal salts such as zinc or copper salts, or salts with ammonia or organic amines, including cyclic amines such as mono-, di- or tri-lower alkylamines, typically hydroxy-lower alkylamines, e.g. mono-, di- or trihydroxy-lower alkylamines, hydroxy-lower alkyl-lower alkylamines or polyhydroxy-lower alkylamines. Cyclic amines are typically morpholine, thiomorpholine, piperidine or pyrrolidine. Suitable mono-lower alkylamines typically include ethyl- and tert-butylamine, and suitable di-lower alkylamines are typically diethyl- and diisopropylamine, and suitable tri-lower alkylamines are typically trimethyl- and triethylamine. Corresponding hydroxy-lower alkylamines are typically mono-, di- and triethanolamine; hydroxy-lower alkyl-lower alkylamines are typically N,N-dimethylaminoethanol and N,N-diethylaminoethanol; a suitable polyhydroxy-lower alkylamine is glucosamine. Unsuitable salts are also included for pharmaceutical usages, as these may be used, inter alia, for the isolation and/or purification of free compounds of formula I and their pharmaceutically acceptable salts.

The compounds of formula I and their pharmaceutically acceptable salts have valuable pharmacological properties.

The novel compounds of formula I have a prolonged stimulating action on beta-adrenergic receptors or they induce relaxation of sensitive unstriated muscles.

Owing to this effective relaxation of unstriated muscles, the compounds of formula I can be used for the prevention or treatment of bronchial spasm and dispnoe in diseases such as bronchial asthma, chronic bronchitis and chronic obstructive pulmonary diseases, anaphylactic bronchial spasm and cystic fibrosis as well as for the prevention or alleviation of premature labour pains in a stage of pregnancy.

The compounds of formula I are also useful for the prevention or treatment of inflammatory conditions in a variety of diseases, especially where the activation of beta-adrenergic receptors influences the course of the disease.

In particular, the compounds of formula I are suitable for preventing or limiting the release of preformed or newly synthesised inflammation transmitters of cellular degranulation products and reactive oxygen compounds of cells such as mast cells, macrophages, basophilic cells, eosinophilic cells and lymphocytes.

The compounds of formula I induce an antiinflammatory action by preventing or limiting the release of phlogogens such as histamine, leucotrienes, basic and cationic proteins, tryptanes and chymase, cytokines and the like, and are suitable for the treatment of chronic and acute urticaria, psoriasis, allergic conjunctivitis, acinitis, hay fever, mastocytosis and the like.

By activating endothelial beta-adrenergic receptors the novel compounds are also suitable for preventing or alleviating the consequences and injury caused by increased microvascular permeability and may be used, inter alia, for inflammations caused by inflammation transmitters, surgical operations, injuries, burns and radiation injury. The compounds are therefore suitable for the treatment of diseases that are associated with obstruction of the respiratory tract such as asthma, chronic bronchitis and other pulmonary diseases, intumescences, extravasations resulting from surgical operations, chemical injuries, burns and also radiation injury such as cerebral oedema and other injury resulting from radiotherapy. By activating the signal transduction mechanism which is coupled to beta-adrenergic receptors, for example adenylyl cyclase (but not restricted thereto), the novel compounds prevent the production of cytokines, lymphokines and also monokines whose synthesis is regulated by easily influenced signal transduction elements, and they are therefore suitable for the treatment of diseases in which proteins participate as transmitters in the course of the disease, including asthma, septicaemia, inflammations, certain immunological processes and the like.

The compounds of formula I induce a useful relaxation of a smooth muscle of the bronchia, of the uterus, of the vascular system and the like.

This relaxation can be detected as follows: in segments which were taken from the ileum of a guinea pig weighing 300-400 g and incubated in an organ bath in tyrode solution at 38° C. and gassed with a mixture of 95% oxygen and 5% carbon dioxide at a load of 1 g, contractions are induced with synthetic leucotriene D₄ (in potassium salt form) or histamine PGE₂α, thromboxane mimetica or BaCl₂ (as depolarising solution) and registered isotonically. The degree of inhibition of the contractions by the test compound is determined after a preliminary incubation of 2 minutes in the form of the IC₅₀, which denotes the concentration at which the test contractions are reduced by 50%.

The compounds of formula I have an extremely prolonged action and exhibit excellent activity in vivo. For example, in a bronchoconstriction standard assay using guinea pigs, a pronounced LTD₄ -antagonistic effect may be observed on administration of an aerosol solution containing c. 0.00001 to c. 1% by weight of test compound. In this test model, male guinea pigs of 400-700 g body weight are anaesthetised intraperitoneally with 1.4 g/kg of urethane and a polyethylene cannula is inserted into the jugular vein. A second polyethylene cannula is inserted into the trachea. Pressure in the oesophagus is recorded by means of a cannula inserted into the oesophagus and connected to a Statham pressure transducer. The animal is placed in an airtight plexiglass chamber which is connected to a No. 000 Fleisch's tube and a Validyne transducer MP 45-1. The flow is measured with this assembly. After the surgical preparation of the test animals, a certain period of time is allowed to elapse so as to allow the pulmonary functions to stabilise. The test compound is then administered in accordance with the following procedure. The test animals are exposed for one minute to a 1% (weight/volume) aerosol solution of the test compound or to distilled water (for control purposes). For all the test compounds that are administered by inhalation, a Monaghan ultrasound spray apparatus (model 670) of which the particle size varies between 1 and 8 microns, the majority being 3 microns, is used. Aqueous solutions are freshly prepared each time and are introduced into the chamber of the spray device using an on-stream drug vial. The spray mist produced is administered to the test animals via a glass chamber of 65 ml capacity which is connected to the trachea by a cannula. At the end of the treatment period, LTD₄ (0.3 μg/ml) is administered over a period of 2 minutes using a second Monaghan ultrasound spray apparatus (model 670) and via a similar glass chamber. The reduction in compliance is read off in the third minute after the LTD₄ administration and the average value of three animals is compared with the average value of three control animals and the percentage inhibition of compliance (% inhibition) is calculated in accordance with the following formula: ##EQU1## If different concentrations of active ingredient are tested, the percentage inhibition for each concentration is recorded, the "log concentration" on the abscissa being plotted against the "percentage inhibition" on the ordinate. The IC₅₀ is then determined by linear regression analysis.

The compounds of formula I and their pharmaceutically acceptable salts also have the specific and therapeutically very significant advantage of a relatively long duration of efficacy.

Preferred compounds of formula I within the scope of this invention are those wherein R₁ and R₂ are simultaneously hydrogen or both are simultaneously methyl or ethyl, and the salts thereof in racemic and chiral form.

Particularly preferred compounds of formula I within the scope of this invention are those wherein R₁ and R₂ are simultaneously hydrogen or both simultaneously are methyl, and the pharmaceutically acceptable salts thereof in racemic and chiral form.

Most preferred compounds of formula I within the scope of this invention are those wherein R₁ and R₂ are simultaneously hydrogen, and the pharmaceutically acceptable salts thereof in racemic and chiral form.

Specifically preferred within the scope of this invention is the racemate obtained in Example 1 of (5R)-3-[6-(4-phenylbutoxy)hexyl]-5-(4-hydroxy-3-hydroxymethylphenyl)oxazolidine and (5S)-3-[6-(4-phenylbutoxy)hexyl]-5-(4-hydroxy-3-hydroxymethylphenyl)oxazolidine or the enantiomers in pure form, or a pharmaceutically acceptable salt thereof.

The invention further relates to a process for the preparation of compounds of formula I and the salts thereof, which comprises reacting a compound of formula II, as racemate or in chiral form ##STR3## wherein R₃ and R₄ are hydrogen, or at least one of the two substituents R₃ and R₄ is a protective group or both substituents R₃ and R₄ are a protective group, with a compound of formula III ##STR4## in free and acetalised or ketalised form, wherein R₁ and R₂ are as defined for formula I, and converting reaction products in which R₃ and/or R₄ may be a protective group into compounds of formula I in which R₃ and/or R₄ are hydrogen.

The protective group R₃ or R₄ may be any known protective group, conveniently one described in "Protective Groups in Organic Chemistry", ed. J.F.W. McOmie (Plenum Press, 1973). Illustrative examples of hydroxyl protective groups R₃ and R₄ are aralkyl groups such as benzyl, diphenylmethyl or triphenylmethyl, and acyl such as acetyl, pivaloyl, 3,5-dinitrobenzoyl or benzoyl.

The removal of the protective group to form a compound of general formula I can be carried out by per se known methods. If, for example, R₃ and R₄ are an aralkyl group, said group can be removed by hydrogenolysis in the presence of a metal catalyst (e.g. palladium on carbon). If R₃ and R₄ are an acyl group, said group may be removed by hydrolysis, e.g. with a base, conveniently an alkali metal hydroxide or alkaline earth metal hydroxide, typically sodium hydroxide or calcium hydroxide.

The condensation of the compounds of formula II with compounds of formula III is carried out in conventional manner in a protic or aprotic solvent such as an aliphatic hydrogen halide, conveniently in a dichloroalkane, preferably methylene chloride, or an aliphatic or cycloaliphatic ether, e.g. in tetrahydrofuran or also dioxane. Other suitable solvents include acetonitrile, ethanol and toluene.

The substances are reacted in the temperature range from -10° to +60° C., preferably from 0° to +30° C., conveniently in the presence of a catalyst, an acid condensing agent, typically an ammonium salt such as ammonium acetate. The starting material of formula II is known and its preparation is described in DE-OS 3414 752.

The compounds are formula III are likewise known and described in all textbooks of chemistry as belonging to the stock of common knowledge.

Compounds obtainable by the process of this invention can be converted in conventional manner into compounds of formula I.

Salts of compounds of formula I can be converted in a manner known per se into the free compounds, conveniently by treatment with a base such as an alkali metal hydroxide, a metal carbonate or a metal hydrogencarbonate, or with another salt-forming base referred to at the outset or with an acid, typically a mineral acid, as with hydrochloric acid, or with another salt-forming acid referred to at the outset.

Salts of compounds of formula I can be converted in a manner known per se into other salts, conveniently by treatment with a suitable metal salt, typically a sodium, barium or silver salt, of another acid in a suitable solvent in which a resultant inorganic salt is insoluble and is thus eliminated from the equilibrium of reaction, and salts of bases by generating the free acid and repeated salt-formation.

The compounds of formula I, including their salts, may also be obtained in the form of hydrates or include the solvent used for crystallisation.

Because of the close relationship between the novel compounds in the free form and in the form of their salts, the references made throughout this specification to the free compounds and their salts will also apply by analogy to the corresponding salts and free compounds.

Depending on the choice of starting materials and procedures, the compounds of formula I and their salts may be obtained in the form of one of the mixtures of diastereoisomers, racemates and enantiomers or as mixtures thereof.

Racemates are separated into the individual enantiomers by column chromatography via a chiral stationary phase.

Racemates can also be separated by known methods into the optical antipodes, conveniently by recrystallisation from an optically active solvent, with the aid of microorganisms or by reacting the mixture of diastereoisomers or racemate with an optically active compound, e.g. depending on the acid, basic or functionally modifiable groups present in the compound of formula I, with an optically active acid, base or an optically active alcohol, into mixtures of diastereoisomeric salts or functional derivatives such as esters, separating these into the diastereoisomers from which each desired enantiomer can be set free in the corresponding usual manner. Bases, acids or alcohols suitable for the purpose are typically optically active alkaloid bases such as strychnine, cinchonine or brucine, or D- or L-(1-phenyl)ethylamine, 3-pipecoline, ephedrine, amphetamine or similar bases which are obtainably by synthesis, optically active carboxylic or sulfonic acids such as quinic acid or D- or L-tartaric acid, D- or L-di-o-toluyltartaric acid, D- or L-malic acid, D- or L-mandelic acid or D- or L-camphorsulfonic acid, or optically active alcohols such as borneol or D- or L-(1-phenyl)ethanol, or optically active isocyanates.

The invention relates also to those embodiments of the process in which a compound obtainable as intermediate in any stage of the process is used as starting material and the remaining steps are carried out, or a starting material is used in the form of a derivative or a salt or, in particular, is formed under the reaction conditions.

The invention also relates to the novel starting materials which have been specially developed for the preparation of the novel compounds, especially those which result in the compounds I described at the beginning as being especially preferred, to processes for their preparation and to the use thereof as intermediates.

The pharmaceutical compositions of this invention which contain the compound of formula I or a pharmaceutically acceptable salt thereof are those for enteral, e.g. oral, and also rectal and parenteral administration to warm-blooded animals, and they contain the pharmacologically active compound alone or together with a pharmaceutically acceptable carrier. The dally dose will depend on the age, sex and individual condition of the patient as well as on the mode of administration.

The compounds of formula I can be formulated for administration in any suitable manner. The invention relates to medicaments which contain at least one compound of formula I or a physiologically acceptable salt thereof and which are formulated for use in human or veterinary medicine. Such compositions may be formulated together with physiologically acceptable carriers or excipients and with additional optional medicaments.

The compounds of formula I can be formulated for administration by inhalation or insufflation, or for oral, buccal, parenteral, topical (including nasal) or rectal administration. Administration by inhalation or insufflation is preferred.

For administration by inhalation, the compounds of formula I are conveniently used in the form of a pressurised aerosol spray pack using a suitable propellant gas.

Such propellant gases or gas mixtures are known per se for the preparation of pharmaceutical aerosols, and typically include saturated hydrocarbons such as n-propane, n-butane or isobutane or mixtures thereof or partially fluorinated or completely fluorinated (perfluorinated) hydrocarbons.

Partially fluorinated hydrocarbons are derived from aliphatic hydrocarbons containing preferably 1 to 4 carbon atoms, typically methane, ethane, propane, n-butane or isobutane, or cycloaliphatic hydrocarbons containing preferably 3 and 4 carbon atoms, typically cyclopropane or cyclobutane, the hydrogen atoms being substituted by at least one fluorine atom and, preferably, at least two fluorine atoms, such that at least one hydrogen atom and thus one hydrocarbon bond remains in the molecule.

Completely fluorinated (perfluorinated) hydrocarbons are derived from the above mentioned aliphatic hydrocarbons of 1 to 4 carbon atoms and the cycloaliphatic hydrocarbons of 3 to 4 carbon atoms by substitution of the hydrogen atoms by corresponding fluorine atoms.

Suitable partially or completely fluorinated hydrocarbons are typically methane derivatives containing 1 to 4, ethane derivatives containing 1 to 6, propane derivatives containing 1 to 8, n-butane derivatives containing 1 to 10, cyclopropane derivatives containing 1 to 6 and cyclobutane derivatives containing 1 to 8, fluorine atoms. In these partially or completely fluorinated hydrocarbons the hydrogen atoms may be in different positions of the hydrocarbon molecule. The following possibilities of isomerism exist for partially fluorinated hydrocarbons:

If the hydrocarbon molecule contains only one hydrogen atom, then in propane and butane derivatives said atom may be in the terminal position or at a link of the carbon chain.

Where the hydrocarbon molecule contains more than one hydrogen atom, still further possibilities of isomerism exist for ethane, propane, n-butane, cyclopropane and cyclobutane derivatives as well as for hydrocarbons containing a greater number of carbon atoms. Some or all of the hydrogen atoms may be in terminal position and some or all may be at one member or at different links of the carbon chains. "Mixed" isomerism is also possible, where the hydrogen atoms of aliphatic derivatives are differently distributed on the terminal carbon atoms and on the same or different links of the carbon chain or are on the same or different carbon ring members of cycloaliphatic derivatives.

It is common practice to use code designations to abbreviate the customary nomenclature and to distinguish between the partially fluorinated hydrocarbons as well as the completely fluorinated hydrocarbons referred to hereinafter. These code designations are explained in Pharmazeutische Technologie, H. Sucker, P. Fuch, P. Speiser (Editor), Thieme Verlag, D-7000 Stuttgart 1978, on page 735, and are likewise applicable to CFCs. It is customary to use suffixes with the letters a, b . . . for the numerous possibilities of isomerism referred to.

Preferred partially fluorinated hydrocarbons are tetrafluoroethane (134 and 134a), trifluoroethane (143a), difluoroethane (152 and 152a) and heptafluoropropane (227).

Alternatively, the compounds of formula I for administration by inhalation or insufflation may be in the form of a dry powder, conveniently as powder mixture, of the compound and a suitable powder base material such as lactose or starch. The powder mixture can be in unit dose form, typically in the form of capsules or cartridges of e.g. gelatin, or in the form of blister packs from which the powder can be released by means of an inhaler or an insufflater.

For oral administration, the pharmaceutical compositions may typically be in the form of tablets, capsules, powders, solutions, syrups or suspensions which are prepared by known methods with acceptable diluents or medicinal carriers. For buccal administration, the composition may be in the form of tablets, drops or lozenges, which are prepared in known manner.

The compounds of formula I can also be administered parenterally. Compositions for injection may be in unit dose form in ampoules or in multiple dosage containers with added preservatives. The formulations may be in the form of suspensions, solutions or emulsions in oil or aqueous vehicles and can contain adjuvants such as suspending agents stabilisers and/or dispersants. Alternatively, prior to use the active compound may be in powder form for reconstitution with a suitable carrier, typically sterilised, pyrogen-free water.

For topical application, the pharmaceutical compositions of this invention may be in the form of ointments, lotions or creams which are prepared in per se known manner, conveniently with an aqueous or oily base, usually by adding suitable thickeners and/or solvents. For nasal application, the compositions can be in the form of a spray which may be formulated as an aqueous solution or suspension or as an aerosol with a suitable propellant.

The compounds of formula I can also be in the form of compositions for rectal administration such as suppositories or retention enemas, conveniently those that contain suppository bases such as cocoa butter or other glycerides.

If the pharmaceutical compositions are prescribed for oral, buccal, rectal or topical administration, they may be associated in per se known manner with dosage forms that permit a controlled or delayed release.

The contemplated dally dose of active compound for oral administration in the treatment of humans is 10 to 500 μg, which may suitably be administered as a single dose. The exact dose will naturally depend on the age and condition of the patient and on the mode of administration. Suitable doses for administration by inhalation (aerosols) or nasal application are from 1-200 μg, for rectal administration from 10 to 500 μg, for intravenous administration from 0.01 to 100 μg, and for topical application from 1 to 1000 μg.

The following Examples will serve to illustrate the invention. Pressures are given in millibars.

EXAMPLE 1

With stirring, 59.92 μl of 36.5% aqueous formaldehyde are added at room temperature to a solution of 0.30 g of (-)-α¹ -[[[6-(4-phenylbutoxy)hexyl]amino]methyl]-4-hydroxy-1,3-dihydroxymethylbenzene (oil, [α]_(D) ²⁰ =-13.3 ±1.9; C=0.535, MeOH) in 10 ml of methylene chloride. The mixture is then stirred for 15 hours at 0°-15° C. The resultant solution is diluted with 15 ml of methylene chloride and the methylene chloride phase is washed with water (2×5 ml) and with a saturated aqueous solution of sodium chloride (2×5 ml), dried over magnesium sulfate and concentrated by evaporation at 20 mbar and 40° C. With stirring, 5 ml of ether/petroleum ether are added to the residue and the precipitated crystals are isolated by filtration. After recrystallisation from cyclohexane, the (-)-3-[6-(4-phenylbutoxy)hexyl]-5-(4-hydroxy-3-hydroxymethylphenyl)oxazolidine melts at 72°-73°. [¹ H-NMR (400 MHZ, CD₂ Cl₂): 7.27 (m,2H), 7.19 (m,2H), 7.17 (m, 1H), 7.13 (d,d, 1H), 7.00 (d,1H), 6.80 (d, 1H), 4.86 (+, 1H), 4.82 (s, 2H), 4.46 (A,B system, 2H), 3.41, 3.38 (2t, 4H), 3.24 and 2.64 (m, 2H), 2.64, 2.57 (2m,4H) 1.7 . . . 1.3 (m, 12H). [α]_(D) ²⁰ =-5.7 ±1,7° (c=0.577, MeOH)

The following compound is obtained in analogous manner: (+)-3-[6-(4-phenylbutoxy)hexyl]-5-(4-hydroxy-3-hydroxymethylphenyl)oxazolidine, in the form of a crystalline powder. [¹ H-NMR (400 MHZ, CD₂ Cl₂)]: identical with the spectrum of the compound of Example 1. [α]_(D) ²⁰ =+6 ±1.6° (C=0.582, MeOH), starting from 0.12 g of (+)-α¹ -[[[6-(4-phenylbutoxy)hexyl]amino]methyl]-4-hydroxy-1,3-dihydroxymethylbenzene in the form of an oil.

EXAMPLE 2

With stirring, 0.18 ml 36.5% aqueous formaldehyde are added at room temperature to a suspension of 0.589 g of (RS)-α¹ -[[[6-(4-phenylbutoxy)hexyl]amino]methyl]-4-hydroxy-1,3-dihydroxymethylbenzene (racemic mixture of R- and S-enantiomers) in 14 ml of methylene chloride. The mixture is stirred for 1 hour, diluted with methylene chloride and stirred for 14 hours at room temperature. The solution is washed with water (2×10 ml), dried over magnesium sulfate and concentrated by evaporation at 20 mbar and 30° C. The residue is dried at 0.1 mbar at 30° C. for 4 hours, giving the racemate of (SR)-3-[6-(4-phenylbutoxy)hexyl]-5-(4-hydroxy-3-hydroxymethylphenyl)oxazolidine in the form of a crystalline powder; m.p. 72°-75° C. [¹ H-NMR (400 MHZ, CD₂ Cl₂)]: identical with the spectrum of the compound of Example 1.

EXAMPLE 3

The (+) and (-) enantiomers of the starting materials of Example 1 are obtained as follows:

1 g of a 1.25% solution in hexane-ethanol (7:1 vol %) of racemic (RS)-α¹ -[[[6-(4-phenylbutoxy)hexyl]amino]methyl]-4-hydroxy-1,3-dihydroxymethylbenzene (also analogously termed (RS)-(±)-4-hydroxy-α¹ -[[[6-(4-phenylbutoxy)hexyl]amino]methyl]-1,3-benzenedimethanol) is charged to a "CHIRACEL OJ" chiral HPLC column (10×50 cm, granular size: 20 μm) (Daicel Chemical Industries, Japan). The column packing consists of silica gel loaded with para-methylbenzoyl cellulose. The enantiomers are separated with a separation factor α=1.28 at a rate of flow of 150 ml/min and with an eluant consisting of hexane (90 vol %), ethanol (10 vol %) and triethylamine (0.1 vol %).

The optical purity of the different fractions is determined by chromatographic analytical separation by means of two HPCL columns (CHIRACEL OJ, 0,46×25 cm) connected in series, using an eluant consisting of (90 vol %), ethanol (10 vol %) and triethylamine (0.02 vol %) at a rate of flow of 1 ml/min.

The column is injected with 3×1 g of racemate and the optically pure fractions are combined and concentrated, giving 1.47 g of the first enantiomer in an optical purity of >99.9%. The fractions enriched with the second eluted enantiomer are further chromatographed until an optical purity of at least 99.8% is obtained. Both chemically impure enantiomers are purified by flash chromatography. The chromatography is carried out on silica gel(granular size 40-63 μm; glass column 2.5×30 cm), in succession with a mixture of a) 250 ml of hexan-ethanol 2:1 (vol %), b) 250 ml of hexane-ethanol 1:3 (vol %), and c) 250 ml of hexane-ethanol 1:6 (vol %) as eluant, at a pressure of 0.2 bar. The pure fractions are collected and then concentrated. The residue is suspended in ether and the suspension is concentrated and dried. The first eluted enantiomer (1.08 g) and the second (0.680 g) are each isolated as an oil and characterised.

First eluted (-)-enantiomer:

(-)-4-hydroxy-α¹ -[[[6-(4-phenylbutoxy)hexyl]amino]methyl]-1,3-benzenedimethanol. Specific rotation (methanol, c=0.535): [α]_(D) ²⁰ -13.3 ±1.9° ¹ H-NMR (400 MHZ, DMSO-D₆, temp. 80° C.: 7.24 (m,3H), 7.15(m,3H), 6.99(d,d, 1H), 669(d, 1H), 4.49 (s, 2H), 4.49 (t, 1H), 3.35 and 3.32 (2t, 4H), 2.50-2.63 (m, 6H), 1.25-1.66 (m, 12H).

Second eluted (+)-enantiomer:

(+)-4-hydroxy-α¹ -[[[6-(4-phenylbutoxy)hexyl]amino]methyl]-1,3-benzenedimethanol. Specific rotation (methanol, c=0.609): [α]_(D) ²⁰ +13.5 ±1.6° ¹ H-NMR (400 MHZ, DMSO-D₆, temp. 80° C.: identical with the spectrum of the (-)-enantiomer. 

What is claimed is:
 1. A compound of formula ##STR5## wherein R₁ and R₂ are simultaneously hydrogen or both together are the identical alkyl radical of up to seven carbon atoms, or a salt thereof in racemic and chiral form.
 2. A compound of formula I according to claim 1, wherein R₁ and R₂ are simultaneously hydrogen or both are simultaneously methyl or ethyl, or a salt thereof in racemic and chiral form.
 3. A compound of formula I according to claim 1, wherein R₁ and R₂ are simultaneously hydrogen or both simultaneously are methyl, or a pharmaceutically acceptable salt thereof in racemic and chiral form.
 4. A compound of formula I according to claim 1, wherein R₁ and R₂ are simultaneously hydrogen, or a pharmaceutically acceptable salt thereof in racemic and chiral form.
 5. The racemate of (5R)-3-[6-(4-phenylbutoxy)hexyl]-5-(4-hydroxy-3-hydroxymethylphenyl)oxazolidine and (5S)-3-[6-(4-phenylbutoxy)hexyl]-5-(4-hydroxy-3-hydroxymethylphenyl)oxazolidine, or a pharmaceutically acceptable salt thereof.
 6. (5R)-3-[6-(4-phenylbutoxy)hexyl]-5-(4-hydroxy-3-hydroxymethylphenyl)oxazolidine, or a pharmaceutically acceptable salt thereof.
 7. (5S)-3-[6-(4-phenylbutoxy)hexyl]-5-(4-hydroxy-3-hydroxymethylphenyl)oxazolidine, or a pharmaceutically acceptable salt thereof.
 8. A pharmaceutical composition comprising, in addition to customary pharmaceutical excipients, a compound according to claim 1 in the free form or in the form of a pharmaceutically acceptable salt as active ingredient.
 9. A process for the preparation of a novel compound of formula I according to claim 1 or a salt thereof, which comprises reacting a compound of formula II, as racemate or in chiral form ##STR6## wherein R₃ and R₄ are hydrogen, or at least one of the two substituents R₃ and R₄ is a protective group or both substituents R₃ and R₄ are a protective group, with a compound of formula III ##STR7## in free and acetalised or ketalised form, wherein R₁ and R₂ are as defined for formula I, and converting a reaction product in which R₃ and/or R₄ is a protective group into a compound of formula I in which R₃ and/or R₄ are hydrogen, and, if desired, separating a mixture of isomers into the individual isomers and isolating the desired isomer and/or converting a free compound into a salt or a salt into the free compound or into another salt.
 10. A process according to claim 9, which comprises separating a racemate of a compound of formula I into the individual enantiomers.
 11. A process according to claim 10, which comprises separating a racemate of a compound of formula I via a chiral stationary phase by column chromatography.
 12. A method of therapeutically treating the human or animal body, comprising administering to said human or animal a therapeutically effective amount of a compound of claim
 1. 